TERRAFORMING TERRA
We discuss and comment on the role agriculture will play in the containment of the CO2 problem and address protocols for terraforming the planet Earth.
A model farm template is imagined as the central methodology. A broad range of timely science news and other topics of interest are commented on.

Thursday, August 18, 2011

Theoretical Breakthrough in Super Conductance

This is a neat breakthrough in
our theoretical understanding of superconductance.The promise now is a rapid development of theory
as it can now be tested against empirical work successfully.Until this it was not happening.

It may take a couple of more years, but it may become possible to predict the
existence of new materials and we may get our room temperature solution yet.

Certainly this appears to be great news in the long development ofthe technology.

Although high-temperature superconductors are widely used in
technologies such as MRI machines, explaining the unusual properties of these
materials remains an unsolved problem for theoretical physicists. Major
progress in this important field has now been reported by physicists at the University of California,
Santa Cruz, in
a pair of papers published back-to-back in the July 29 issue of PhysicalReview Letters.

The first paper, by UCSC physicist Sriram Shastry, presents a new
theory of "Extremely Correlated Fermi Liquids." The second paper
compares calculations based on this theory to experimental data from studies of
high-temperature superconductors using a technique called angle-resolved
photoemission spectroscopy (ARPES). The lead author of this second paper is
Gey-Hong Gweon, assistant professor of physics at UC Santa Cruz, with coauthors Shastry and Genda
Gu of Brookhaven NationalLaboratory.

"I showed my preliminary calculations to Gweon, who is an expert
in this field, and he was very excited," said Shastry, a distinguished
professor of physics at UCSC. "He obtained data from lots of
experimental groups, including his own, and we found a remarkably successful
agreement between theory and experiment at a level that has never been achieved
before in this field."

Shastry's theory provides a new technique to calculate from first
principles the mathematical functions related to the behavior of electrons in
a high-temperature superconductor. Interactions between electrons, which
behave as almost free particles in normal metals, are a key factor in
superconductivity, and these electron-electron interactions or correlations are
directly encoded in photoemission spectra.

Photoemission spectroscopy is based on the photoelectric effect, in
which a material emits electrons as a result of energy absorbed from light
shining on the surface of the material. ARPES studies, which produce a spectrum
or "line shape" providing clues to the fundamental properties of the
material, have yielded anomalous results for high-temperature superconductors.

"The unusual 'fatness' of the line shapes observed in electron
spectroscopy has been at the center of the mystery of high-temperature
superconductors," Gweon said. "The anomalously broad and asymmetric
line shape has been taken as a key signature of strong electron-electron
interaction."

Shastry's theory of extremely correlated Fermi liquids is an
alternative to the Landau Fermi liquid theory, which is a highly successful
model for the weakly interacting electrons in a normal metal but not for very
strongly correlated systems.

The success of Shastry's calculations indicates that the anomalous
photoemission spectra of high-temperature superconductors are driven by extreme
correlations of electrons. Shastry coined the term "extreme
correlation" to describe systems in which certain "energy
expensive" configurations of electrons are prohibited. This arises
mathematically from sending one of the variables, known as the Hubbard
"U" energy, to infinity.

"That leaves you with a problem that is very hard to solve,"
Shastry said. "I have been studying these problems since 1984, and now I
have found a scheme that gives us a road through the impasse. The spectacular
correspondence with the experimental data tells us that we are on the right
track."

The experimental data come from ARPES studies using two different
sources of light: high-energy light from synchrotron sources and lower-energy
laser sources. In studies of high-temperature superconductors, these two light
sources yield significantly different photoemission spectra for the same
samples, and researchers have been unable to resolve this inconsistency.

But Gweon and Shastry found that these apparently irreconcilable
results can be accounted for by the same theoretical functions, with a simple
change in one parameter.

"We can fit both laser and synchrotron data with absolute
precision, which suggests that the two techniques are consistent with each
other," Shastry said. "They are telling two different slices of the
same physical result."

Shastry said he plans to use the new technique to calculate other
experimentally observed phenomena. "There is still a lot of work to be
done," he said. "We have to look at a variety of other things, and
extend the new scheme to do other calculations. But we have made a breach
through the impasse, and that's why we are excited."

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About Me

Apr 2017 - 4.1 Mil Pg Views, March 2013 - Posted my paper introducing CLOUD COSMOLOGY & NEUTRAL NEUTRINO rigorously described as the SPACE TIME PENDULUM, September 2010 I am pleased to report that my essay titled A NEW METRIC WITH APPLICATIONS TO PHYSICS AND SOLVING CERTAIN HIGHER ORDERED DIFFERENTIAL EQUATIONS' has been published in Physics Essays(AIP) and appeared in their June 2010 quarterly. 40 years ago I took an honors degree in applied mathematics from the University of Waterloo. My interest was Relativity and my last year there saw me complete a 900 level course under Hanno Rund on his work in relativity,as well as differential geometry(pure math) and of course analysis. I continued researching new ideas and knowledge since that time and I have prepared a book for publication titled Paradigms Shift&. I maintain my blog as a day book and research tool to retain data and record impressions and interpretations on material read. Do join my blog and receive Four items of interest daily Monday through Saturday.